Reactor with adjustable stator blades



Dec. 21, 1954 J, FEATQNBY 2,697,326

REACTOR WITH ADJUSTABLE STATOR BLADES Filed April 30, 1951 United States Patenti() REACTR WITH ADJUSTABLE 'STA-TORBLADES Joseph Featonby, Ottawa, Ontario, Cannda,assignor to National Research Council, Ottawa, ntario, Canada, a corporation olf-Canada Appiicancn April 3o,.19's1,.sea1fNu. 223,673

4 claims. (01.60-39.25)

This invention relates generally to reactors, and more particularly to means for varying the angles vof attack of at least some yof the stator lblades ofa reactor. .By the term reactor, as used in this'speciication 'and claims, I mean any vsteam or internal combustion turbine orcompressor. ,j

It has been appreciated by designers `vof "reactors for vmany years that a substantial improvement in performance and eiciency is obtainable by varying'the angles of attack of the `stator blades (i.'e. varying the nozzle openings) in accordance with the ,loading of the reactor. v

The provision of variable nozzleopenings permits 'of .rotor and `stator blading 'design which yields a-'higher efficiency with a lower Mach number at the entry tothe rotor blading. vWhere 'the angles 'of attack of the `stator blades are variable, the probability of 'reaching' the choking point in, say, a high compression lratio turbine would be greatly reduced and blow olf 'instarting may 'be obviated.

Despite these attractive possibilities, it is s'tillnornial practice to design reactors with the angle of 'attack of the stator blades iixed, since no simple practical 'means has been provided for varying .the nozzle openings ac cording to load. I am well aware that there have lbeen `many proposals for accomplishing this desirable variation of the blades, but none of the'prior proposals known to me have been sufliciently simple and effective to lead to any wide acceptance. y

In contrast to these complicated mechanical `adjust ing devices which are controlled manually or by temperature responsive devices, I adjust the angles of 'attack of'stator blades of a reactor by meansof a Simple mechanical arrangement which is directly Vactuated in a positive manner by the thermal growth ofthe reactor,

fa factor which has previously been "regarded only as a handicap in the design of turbines and compressors.

It is interesting to note that, while,as pointed out above, it has been known for years that itwouldbe `-advantageous to be able to vary the nozzle openings, it is today vcommon practice Vto use non-:adjustable stator blades 'and 1to give the lleading edges of the rotor blades a greater thickness Athan the optimum for `eciency in order "that the `reactor `may give a 'reasonable performance olf' the design point. With this compromise, 'whenjthereacto'r 4is running off the design point, the rotor blades oler a better angle of reception to the lgases ilowin'g from the reactor nozzles, but the efiiciency of "tl'i'e reactor'atits Vdesign point is reduced due yto theincreased thickness of the leading edges of the rotor blades and the 'con'- sequent reduction of the area `for passage "of the gases.

yThe relative Mach number is increased and "may become critical. That this unsatisfactory 'compromise is tolerated, is, I feel, evidence that the `prior .proposa'lsjfor varying the angles of attack of 'stator blades are either 4inoperative or complicated to the point of impracticability.

My simple proposal ffor 4uti-lizingxthe ,thermal growth of the reactor components to vary the nozzle `openings with temperature permits rotor blade design which offers a more eilicient reception angle to the gases owing -to the rotor blades from the adjustable stator blades. Irn- A tit) proved 'performance both at and off the design 'point .results from `my proposal.'

vThe apparatus Yaccording 'to 'iiyivention-fmayfgem' erally be defined as a 'r'ea'c'tor having at least one 'stage' of stator blades and at least one stage of cooperating rotor blades, a plurality of the blades in at least one of *passed "-fo meniber 15,

2,697,326 Patented Dec. 2l, 1954 2 the vstatoristages being adjustable, and means for varying theanglesof attackfof `the `adjustable blades compris'ing'meansfor' mounting each of the adjustable blades to rotate about '-a'n axis 'which V"is'tixed with respect to the *stator 'casing-an element projecting'ffrom each adjustable blade, v'and inearis Vfor mounting said projecting elements .for-"controlledsliding-:movement in afportion of the structuresubstantially -diiferently affected by the heat developed during operation of the vreact'orthan the ystator easing, the two said 4mounting means cooperating to .rotate the adjustable blades and vary the ow characteristicsthiough the ireactor as Vthermal growth of the reactor "causes relative movement of the stator casing and 'said portion I'propose vto describe in vvdetail two embodiments of the invention as applied to a turbine. It should be appreciatedhowever, that the invention may be applied rwith-fadvanta'get't'o the vadjustment of statorblades in a compressor, fandf an example o'f'such 'an application will be br-ie'ily set Aout -liereinafte'n -In drawings which illustrate TVembodiments of the involition applied to "turbines:

Figure 1 is Ya side'elevatiom partly broken away, 'of `an'embodirrient in which axial thermal growth is utilized, Figure 2'is-"a detail of one of the slots fof the embodi- 'ment sh'ovvn in Figure f1, K Figure 3 is alfragmentary section of a second embodifmeiitfinwhichlradial thermal lgrowth is utilized, 'Y igure 4 is "a 4sectio'rro'n the y'line A-A of Figure 3, an

Figni'eSis *ad'e'tail of one of thes'lots vof the embodinient shown in Fgure 3. l y

lReferring vfirst toFigures l and 2, lreference numeral 1.0 indicates the -wall of the combustion vchamber of a Y:gas-turbine, I1 v'indicates the vouter stator casing, and 12 the Vinner stator casing. A plurality V`ot stator blades, one lof which lis'indicated lat 13, "extend between the two stator casings andare each mounted to rotate about an 'axis which "is fixed r with respect to the stator casing. iA circular flange 14"extends aroundthe combustion charnberatthe end V'adjacent-the stator, the ange'being rigidly secured to thecom'busto'n chamber wall 10. A tubular member 15'is-'secured to flange 14 by means of a row of pins 15a which projectradially fromfthe flange, and extend througha row Vof slots 15b formed at one end of Lnieinber A15. 'Slots 15b tare elongated transversely of member 1`5, so`=that tubular member 15 is permitted lim- "itedr'otationalmovement with respect to ilange 1'4. The *reason such movement 'is provided for `will appear hereinafter., Tubular Amember l15 is generallyconcentrically disposediwith "respect to the stator casing, being spaced *some distance'foutwardly therefrom and enveloping the eoute'r casingll. Member A15 is provided with a second series "-o'f slots 16, which, while they may be generally 'described fas longitudinal yslots (since they extend generally parallel to the longitudinal faxis'of the stator) are actuallyarcuatelycufrved vrin a direction which is an- Y'g'iilar with 'respect 4to thelstator axis. j IBlade 13 is mounted `vfor `rotation `within the 'stator casing by'a cylindrical boss 1`7dispo'sed "within a cylin- Vdricall'reosl's in :casing 12 -and Va cylindrical boss 18 'which :is vreceived 'in `a cylindrical recess `in Vouter casing 11. Bosses 17 'and '1'8 are preferably integral with the blade 13,`but"rein'any event ixed with respect thereto. A 'rod-like member z1 9 projects Iaxially from, and is rigidly secu-redto LVA(for-is integral with) fboss I8, so that rotation fof Lprojecting member v19 will VAbring about rotation of lblade 13 'about'an axisjwhich is'xed with respect to the stator casing.y One4 side tof 'projecting member 19 is yflattenedoverthejend'portion-thereof as indicated at 19a. YTheliiattened 'end 19a 'of each'member 19 extends through one'o'fjthe arcuate slots -16 in member V15, 'and is snugly lengaged by itl-re sides offth'ev slot.

The combustioncha'mber .10 "and 'the 'stator casing are connected to one another Abymeans of 'an expansion joint '20. :By virtueiof this joint, 'while 'any axial` expansion for Icontraction :ofq combustion 'chamber ,10 is `directly Asuch movement "'s tak'en up by the expansion joint 20, and is therefore inot vimparted 'to the stator casing 11. Heating or cooling of the combustion chamber 10 therefore causes relative axial movement of slots 16, and the blades the member (having the slots 16) and the outer stator casing 11. As the slots 16 move n the influence of temperature changes in the combustion chamber 10, the flattened end portions 19a of projecting members 19 are forced to follow the curving of the 13 are forced to rotate. The amount of rotation imparted to the blades is governed by the temperature range of the combustion chamber, the coefficients of expansion of the metallic members affected by the temperature changes, and the degree of curvature of the arcuate slots. As slots 16 move back and forth, the curvature of the slots brings about rotation of member 15 with respect to ange 14, the movement being permitted by sliding of pins 15a in the transversely elongated slots 15b.

While Figure l illustrates turning of but one stage of stator blades, it will be appreciated that any number of stages may be adjusted in similar fashion merely by extending member 15 and providing additional rows of slots 16.

Turning to Figures 3, 4, and 5, 21 indicates the outer stator casing and 22 the inner stator casing of a turbine, while 23 is a stator blade which is mounted for rotation back and forth under about an axis which is fixed with respect to the stator,

the mounting means consisting of cylindrical bosses 24 and 25 fixed to opposite ends of blades 23 and seated in cylindrical recesses in outer casing 21 and inner casing 22 respectively. Bosses 24 and 2S are preferably integral with blade 23, but are in any event xed with respect thereto. A rod-like member 26 projects axially from boss 24, passing through casing 21 and projecting therewithout. A collar 27 is fixed to projecting member 26 where the latter emerges from stator casing-21;and two diametrically opposed transverse projections 28 extend from projecting member 26 adjacent the free end thereof.

A sleeve 29 is mounted in a portion of the structure relatively unaffected by the heat developed during operation of the turbine, and two similar but diametrically opposed arcuate slots 30 are provided in the sides-of sleeve 29. Slots 30 are slightly wider than the diameter of the projections 28. The free end of projecting member 26 is disposed within sleeve 29, with the projections 28 riding in the arcuate slots 30. (Sleeve 29 is partable for assembly purposes as indicated at 31 in Figure 4.) A plurality of stator blades may be adjustably mounte as described above in connection with blade 23 and the angle of attack of these blades is varied in accordance with the temperature of the motive gases in `the following manner. The hot gases passing relatively unaffected by the heat developed and will remain at a relatively fixed radial distance from the longitudinal axis of the stator casing. Radial outward expansion of outer stator casing 21 moves collar 27 outwardly and projecting member 26 is carried further into sleeve 29. As member 26 penetrates sleeve 29 more deeply the projections 28 are forced to slide in the arcuate slots 30, and the curvature of the slots forces projecting member 26 to rotate. Rotation of projecting member 26 in turn rotates the blade 23.

It will be appreciated that where radial expansion of the stator casing is used to impart rotation to the stator blades as described above, allowance must bel made for the axial expansion of the stator casing `since projections 28 are riding in a portion of the structure relatively unaffected by the expansion. With this in view, sleeve 29 is so mounted that it is movable longitudinally ofA the stator, but radical movement or rotation-is prevented.

Since the outer stator casing 21 will expand and con-` tract in advance of the inner casing 22, I recommend that a clearance, as indicated at 32, be left between the blade 23 and the inner stator casing 22 to avoid damage of the blade. (Some similar precaution should also, of course, be taken in the case of the blades 13 of Figure l.)

Radial outward expansion of casing 21 in advance of casing 22 introduces a problem of leakage between the inner end of blade 23 and the inner casing 22. This leakage may be avoided by increasing the diameter of boss 25 so that the enlarged boss shrouds the area where leakage might'otherwise occur. If, however, the bosses 25 of adjacent blades were enlarged sufficiently to completely shroud the area of potential leakage, they would interfere with one another. .q

through the turbine cause turbine casings 21 and 22 to expand. Sleeve 29 will be i I should also like to point to the advisability of leaving adequate clearance between projecting member 26 and sleeve 29 on the one hand and between projections 28 and slots 30 on the other hand, since otherwise binding may occur due to the fact that elements 26 and 28 are more affected by heat than the sleeve and its slots. Suicient clearance to avoid binding due to differing rates of expansion should also, of course, be provided between the flattened end portions 19a of projecting elements 19, and the arcuate slots 16, in the case of the embodiment shown in Figures l and 2.

Referring again to the structure shown in Figures l and 2, I would like to point out that generally similar principles utilizing axial thermal growth may be applied to automatic adjustment of the stator blades of a compressor.

What I claim is:

l. A reactor including a combustion chamber, a bladed rotor, an. outer stator casing, an inner stator casing, an expansion joint between said combustion chamber and said outer stator casing, a tubular member secured to said combustion chamber adjacent the expansion joint and enveloping said outer stator casing, a plurality of adjustable stator blades rotatably mounted in said stator by means of bosses fixed to the opposed ends of said blades and recesses in said inner and outer casings for thc reception of said bosses, an element projecting radially from each adjustable blade, said projecting elements having flattened end portions, and a series of arcuate generally longitudinally extending slots in said tubular member, the flattened end portions of said projecting elements passing through said slots, said attened end portions riding in said arcuate slots and imparting rotation to said rotatably mounted `blades as axial thermal growth of the reactor causes relative movement of said tubular member and said stator casing.

2. A turbine or compressor apparatus comprising a combustion chamber, a stator casing, at least one stage ofstator blades, a plurality of the blades in at least one of the stator stages being adjustable, and means for varying the angles of attack of the adjustable blades comprising a tubular casing surrounding said stator casing and spacedoutwardly therefrom, an expansion joint between the combustion chamber and said stator casing, a mechanical connection between the combustion chamber and the other of said casings whereby axial thermal growth of said combustion chamber is imparted to said tubular casing, the presence of said expansion joint and said connection causing said stator casing and said tubular casing to move relative to one another whenever there is'an appreciable change in the temperature of said gases, means secured to each of said adjustable blades and mounted in said stator casing whereby each adjustable blade is rotatable about an axis which is fixed with respect to the stator casing, an element projecting from cach of said rotatably mounted adjustable blades, and a plurality of arcuate guide slots in said tubular casing, said projecting elements being operatively connected with said guide slots, said guide slots being arranged to dictate the direction of movement ofsaid projecting elements with respect to said tubular casing and impart rotation to the rotatably mounted blades whenever thermal growth of the apparatus causesrelative movement of said tubular casing and said stator casing. 3. An apparatus as defined in claim 2, in which all the blades of one stage are adjustable.-

4. An apparatus as defined in claim 2, in which said guide slots extend generally longitudinally in said tubular casing and in which said projecting elements have fiattened end portions, said flattened encl portions riding in said slots and imparting rotation'to said rotatably mounted blades as axial thermal growth of the apparatus causes relative axial movement of said tubular casing and said stator casing.

References Cited in the tile of this patent UNITED STATES PATENTS 2,428,830 Birmann Oct. 14, 1947 

